Locking device for an adjustment unit of a motor vehcile seat

ABSTRACT

A locking device for an adjustment unit of a motor vehicle seat having a toothed bar, a locking part cooperating with the toothed bar, a spring that abuts the locking part and a base part. The locking part comprises at least one tooth for engaging the toothed bar. A mass body is associated with the locking part and is hinged to the base part for pivotal movement about an axis. The mass body has a control contour which comprises a) a flat bight portion with a base, b) at least one enabling inclined portion adjoining the bight portion, c) a transition region adjoining the enabling inclined portion and d) one retaining inclined portion adjoining the transition region. The spring fits at one abutment end against the base of the control contour in the normal position of the locking part; the abutment end is capable of moving along the control contour.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to German Application No. DE 10 2007 059 012.3, filed Dec. 6, 2007, which is hereby incorporated by reference in its entirety as part of the present disclosure.

BACKGROUND OF THE INVENTION

The invention relates to a locking device for an adjustment unit of a motor vehicle seat, in particular for an adjustment unit in the form of a hinge mounting, with a toothed bar, with a locking part cooperating with this toothed bar and with a spring that abuts the locking part and a base part, said locking part comprising at least one tooth for engagement into the tooth bar and a mass body being associated with said locking part, said mass body being hinged to the base part for pivotal movement about an axis. Such a locking device is known from U.S. Pat. No. 5,882,080.

The locking device works depending on acceleration and stops the adjustment unit in the event of a crash. In case of accelerations that are lower than in the event of a crash the locking device remains in its normal position. In this normal position, it is inactive, it does not stop the adjustment unit. The adjustment unit can be a lengthwise adjustment unit such as a rack and pinion; it being preferred that it be an adjustment unit that works about a pivot axis and is generally referred to as a hinge mounting. Preferably, the adjustment unit is a seat back hinge mounting. It is particularly utilized on hinge mountings that are only stopped on one side for stopping the passive seat side.

The value of the acceleration above which the locking device automatically enables and which occurs in the event of a crash, is adapted to the enabling threshold for other safety devices such as airbags.

There is a need for automatically engaging locking devices which stop a hinge or a linear adjustment unit when accelerations occur, which are due to an accident, and which, once adopted a locking position, also remain in this position. The problem with the locking devices is that a locking part moved due to acceleration comes into engagement with the teeth of the toothed bar but bounces back more or less elastically from the toothed bar, meaning comes out of engagement therewith, due to the movement impulse.

The reader is additionally referred to the following prior art documents DE 40 31 285 A1, DE 27 47 584 A1, DE 196 37 658 B4 and DE 103 06 827 B4.

It is therefore an object of the invention to further develop the locking device of the type mentioned herein above in such a manner that it remains in the locking position once it has adopted it. A short-time locking is thus ensured and it is also ensured that the locking position is permanently maintained.

SUMMARY OF THE INVENTION

This object is achieved in view of the locking device of the type mentioned herein above by the fact that the mass body comprises a control contour which comprises a) a flat bight portion with a base, b) at least one enabling inclined portion adjoining said bight portion, c) a transition region adjoining said enabling inclined portion and d) one retaining inclined portion adjoining said transition region, the spring fitting at one abutment end against the base of the control contour in the normal position of the locking part, this abutment end being capable of moving along the control contour and moving from the base to the retaining inclined portion in the event of a crash.

On this locking device, the abutment end of the spring moves relative to the locking part. The locking part has a control contour. The abutment end abuts this control contour. It can move alongside the control contour. Once it has overcome the transition region and has reached the retaining inclined portion, it cannot come back. Then, the locking part is in a position in which it is retained through the spring in engagement with the toothed bar. As a result, secure engagement is achieved on the one side; on the other side, the locking part is prevented from elastically bouncing back from the toothed bar, which is no longer possible.

After an accident lying above a crash threshold, the locking device must first be set back. As long as it is not set back, it is engaged and stops.

The base extends at right angles to the direction of the force with which the spring acts onto the base. Preferably, the base extends over a short distance of about 1 mm to about 4 mm. It is thus achieved that a relative movement between the base and the abutment end occurs, even at the smallest accelerations. As a result, the locking part always keeps slightly moving, even if it only moves a small distance. Anyhow, it thus remains permanently in operation.

The enabling inclined portion adjoining the base is dimensioned such that a certain force or a certain torque is needed for the abutment end to be allowed to move along the enabling inclined portion against the action of the spring. This region is dimensioned such that the desired enablement of the locking device is achieved at a certain acceleration value.

Once the abutment end has moved along the enabling inclined portion and has reached the transition region, it glides on the retaining inclined portion. The transition region can have sharp edges and may for example be configured as the tip of a saw tooth; but it may also be configured to be rounded. It is configured such that no new demands are placed on the movement of the abutment end. Once the abutment end has reached the end of the enabling inclined portion, it is intended to reach the retaining inclined portion under the action of its impulse or the shape of the control contour, meaning to glide therefrom. Once it has reached the retaining inclined portion, the return path is blocked. The return path is cleared by setting it back, manually or otherwise. Usually however, the vehicle seat is damaged to such an extent after an accident that it must be replaced anyhow so that setting back is obsolete.

In a preferred developed implementation, the retaining inclined portion has a smaller angle with respect to the base than the enabling inclined portion. The retaining inclined portion extends for example at an angle of about 10 to about 30° with respect to the enabling inclined portion. The retaining inclined portion thereby extends at a significantly larger angle of more than about 45°, preferably of approximately 90°, with respect to the base. The angle at which the enabling inclined portion is inclined with respect to the base is larger than the angle of self-locking of the materials used.

In a preferred development, the spring is a leg spring; however, it should be noted that other types of springs may be used. The leg spring is preferred because it is easy and inexpensive to manufacture ant its spring force is very precisely given. This also applies for serial production, as it is generally the case on motor vehicle seats.

In order to have particularly defined conditions, it is proposed to provide a guide opening in the base part and to guide the abutment end, meaning the free end of the leg spring, in this guide opening. As a result, precise conditions are provided. Preferably, the abutment end does not abut the walls of the guide opening. The abutment end is however retained within the control curve during movements and accelerations.

There is preferably provided a roll body that is interposed between the abutment end of the spring and the control contour. For the functioning of the locking, which depends on acceleration, it is important to exactly know the friction the abutment end is subjected to when moving along the control curve, in particular along the enabling inclined portion. Through roll friction, very defined friction conditions are provided. Also, it is preferred that the surface of the abutment end and/or of the control contour, in particular of the enabling inclined portion, be coated such that given friction conditions are permanently provided and also respected. This also allows to reach and thus to maintain the precision of the engagement of the locking device at a given acceleration.

Preferably, the control contour is symmetrical to a plane through the contact point of the spring with the base and the direction of the spring force, this plane extending parallel to the axis of the mass body. Thus, the conditions are the same in the event of a rear impact collision and of a frontal crash. It is however also possible to individually adjust the conditions for a frontal crash and for a rear impact collision. By varying the slope of the enabling inclined portion, different acceleration values at which enabling occurs can be given.

In a preferred developed implementation, mass body and locking part are not only in moving communication but are also joined together to form one piece; they are in particular made from one piece. This facilitates mounting. The spring can be a traction spring or a compression spring.

Other features and advantages of the invention will become more apparent upon reviewing the remaining claims and the following non restrictive description of embodiments of the invention, given by way of example only with reference to the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1: shows a simplified illustration of a motor vehicle seat in a side view and with the locking device operating due to the incline.

FIG. 2: shows an enlarged view of a portion of FIG. 1, namely the region below the seat back.

FIG. 3: shows the illustration like FIG. 2, but now in a crash condition.

FIG. 4: is a top view of the mass body according to the FIGS. 1-3, which is shown to a larger scale.

FIG. 5: is a simplified side view like FIG. 1 for a second exemplary embodiment.

DETAILED DESCRIPTION OF THE INVENTION

Of an actually known motor vehicle seat, only the essential elements are shown in the figures. There is shown a seat carrier 20 that is carried by an underframe. In a first exemplary embodiment according to the FIGS. 1 through 4, the underframe is formed by one pair of rails with a top rail 22 and a bottom rail 24 as well as by a rear rocker 28 and a front rocker 30. The bottom rail 24 is provided to be fastened to an underbody (not shown) of a motor vehicle. The seat carrier 20 carries a seat part 26.

At the back, the top rail 22 is hinge-linked to the seat carrier 20 through the rear rocker 28. At the front, the top rail 22 is hinge-linked to the seat carrier 20 through the front rocker 30. Generally, a four-bar linkage is formed. It is stopped in a known way through a toothed bar in the form of a arcuate toothed region 32 that is centered with respect to a rear rocker axis. A stopper part, such as a pinion that is rotatable with an eccentric mounting, is associated with said arcuate toothed region 32. The stopper part (not shown) is actuatable either by hand or by a motor. A locking part 36 that is best shown in the FIGS. 2 and 3 cooperates with the toothed bar 32. It is configured to have two-fold symmetry and has two teeth 38 on either side. It is pivotal about an axis 40; this axis is provided on a base part 42 that is formed here by a seat side part of the seat carrier 20.

A mass body 44 is associated with the locking part 36 and is connected therewith; in one embodiment, it is at least linked for common motion therewith. The mass body 44 is also pivotal about the axis 40. In the implementation according to the FIGS. 1 through 3, the two parts 36, 44 are shown as individual parts that are joined together. In one embodiment these two parts are made from one piece; however, the parts may also be configured as two pieces, which has the advantage that the locking part 36 can be located in the plane of the toothed bar 32, whilst the mass body 44 is lower so that it has space to move. Preferably, the mass body 44 is sheltered so as not to be blocked by foreign parts.

The mass body 44 substantially has the shape of an equilateral triangle; the axis 40 is located in proximity to an angle of the triangle. The mass body 44 extends substantially in the negative z direction. Its mass center 46 is located at a significant distance from the axis 40. In an alternative, it can also extend upward in the positive z direction. As far as practicable, it should be disposed for an acceleration force, which acts in the x direction or in the negative x direction, to be capable of exerting the greatest possible torque onto the mass body 44. This is the case if the line connecting mass center point 46 and axis 40 substantially extends at right angles to the x direction.

The mass body 44 or alternatively the locking part 36 has a control contour 48. In the embodiment shown, it has two-fold symmetry and is approximately formed in the shape of an M. It has a central base 50. This base is located on either side of a plane of symmetry 52, which is defined by the axis 40 and the centerpoint of the base 50. In its center, the base 50 extends at right angles to this plane of symmetry 52. Adjoining this center, it also extends at right angles or in a slight ascending slope, in any case at a very small angle, such as less than 12°. The base 50 is quite short; it is at the most about 2 mm to about 5 mm long. An enabling inclined portion 54 adjoins the base 50 on either side. The contour rises with respect to the base 50 at an angle of about 30° toward the outside. A transition region 56 adjoins the enabling inclined portion 54. In the exemplary embodiment, it is configured to be curved in a convex shape. A retaining inclined portion 58 adjoins it toward the outside. It extends at an angle of about 60° with respect to the enabling inclined portion 54 or at an angle of about 60° or more with respect to the base 50. The retaining inclined portion 58 is part of a bight portion that is rounded toward the axis 40 and is bounded by an outer inclined surface. Also, the base 50 and the two enabling inclined portions 54 form a central bight. Generally, the control contour thus has bight portions arranged in a side-by-side relationship.

There is provided a spring 60 that is configured to be a leg spring. It is placed onto a bolt 62 that protrudes from the base part 42. Its one leg abuts a limit stop 64 that is also formed on the base part 42. The other leg has an abutment end 66. At this end, it abuts the control contour 48. This abutment end 66 is formed by a free end of the leg that is angled at a right angle. It extends across the plane of the drawing. It extends through a guide opening 68 that is provided in the base part 42.

In the normal position of the locking part 36 shown in the FIGS. 1 and 2, the abutment end 66 abuts the base 50; it is exactly in the center on the base 50. The spring force exerted extends in the plane of symmetry 52. The base 50 can be so short that it only can receive the abutment end 66; it may however also be about 2 to about times the width of the abutment end 66.

In FIG. 3, the condition after an acceleration due to a crash is shown. The abutment end 66 is now at the retaining inclined portion 68; at the same time it abuts the lower end of the guide opening 68. The condition shown is stable. The locking part 36 cannot pivot back, the retaining inclined portion 58 being too steep therefore and it cannot pivot further in the direction of engagement either, this being blocked by the engagement of the two teeth 38 with the toothed bar 32.

In a second exemplary embodiment shown in FIG. 5, the mass body 44 substantially consists of a round plate and of a shaft, the axis 40 being provided on the shaft. The locking part 36 is formed by teeth that protrude outward from the mass body 44. They cooperate with a toothed bar 32 that is centered on the pivot axis of a seat back hinge. The normal position is shown.

Underneath the axis 40, the mass body 44 still has a short portion of the shaft, which is used for controlling the locking of the invention. In the base part 42, a spring-loaded ball 70 is retained in proximity to the axis 40; it is located in a bore in the base part 42, which is smaller than the diameter of the ball. The mass body 44 forms a fork at the bottom, said fork having two tines. Between these two tines, there is located the base 50 against which the ball 70 abuts. The inner edges of the tines form the enabling inclined portions 54. If the mass body is sufficiently deflected from its normal position shown, the ball 70 is pushed so far downward that is gets underneath the tines where there is located the transition region 56. Next, the ball snap-fits into a lower recess of every single tine, which is not visible; there, there is the retaining inclined portion 58.

Instead of employing the ball 70, the previously described leg spring 60 can be utilized, for example, in the same or similar manner as indicated above. When the leg spring 60 is employed, the abutment end 66 will then coincide with the position of the ball 70. 

1. A locking device for an adjustment unit of a motor vehicle seat comprising: a toothed bar, a locking part cooperating with said toothed bar, a spring that abuts said locking part and a base part, said locking part comprising at least one tooth for engagement into said toothed bar and a mass body, said mass body is associated with said locking part and is hinged to said base part for pivotal movement about an axis, wherein said mass body has a control contour, said control contour comprises a) a flat bight portion with a base, b) at least one enabling inclined portion adjoining said bight portion, c) a transition region adjoining said enabling inclined portion and d) one retaining inclined portion adjoining said transition region, in a normal position of said locking part said spring fits at one abutment end against said base of said control contour, said abutment end being capable of moving along said control contour and moving from said base to said retaining inclined portion in an event of a crash.
 2. The locking device as set forth in claim 1, wherein said base extends at a right angle with respect to a direction of a force, and the spring acts onto the base with said force.
 3. The locking device as set forth in claim 1, wherein said retaining inclined portion extends at a first angle with respect to said base, said enabling inclined portion extends at a second angle with respect to said base, a course of said enabling inclined portion intersects a course of said retaining inclined portion at an acute angle, and an angle between said base and said enabling inclined portion is smaller than an angle between said base and said retaining inclined portion.
 4. The locking device as set forth in claim 1, wherein said spring is a leg spring.
 5. The locking device as set forth in claim 4, wherein a guide opening is provided in said base part, said leg spring has a free end, and said free end of said leg spring engages into said guide opening.
 6. The locking device as set forth in claim 1, wherein at least one of said control curve and said spring comprise a coating that fixes a definite value of friction.
 7. The locking device as set forth in claim 1, wherein a roll body is provided, said roll body is placed onto said abutment end of said spring.
 8. The locking device as set forth in claim 1, wherein said control contour is symmetrical with respect to a plane through a contact point of said spring with said base and a direction of the spring force, said plane extending parallel to said axis.
 9. The locking device as set forth in claim 1, wherein said toothed bar has tooth flanks, said at least one tooth of said locking part abuts said tooth flank in an event of a crash, said tooth flank extends substantially perpendicular to a line connecting said tooth flank with said axis, the difference between substantially perpendicular and a right angle lying within the angle of self-locking between the materials used.
 10. The locking device as set forth in claim 1, wherein said mass body has a region of large mass located beneath or above said axis in a z-axis direction.
 11. The locking device as set forth in claim 1, wherein said at least one retaining inclined portion is inclined at one of an angle of •20°, •10° and at an angle of less than an angle of self-locking of the materials used, with respect to a radial to said axis, said radial intersecting said retaining inclined portion.
 12. The locking device as set forth in claim 1, wherein said locking part and said mass body are joined together to form one piece.
 13. A locking device as set forth in claim 1, wherein said locking device is a device for an adjustment unit in the form of a hinge mounting.
 14. The locking device as set forth in claim 1, wherein said locking part and said mass body are made from one piece. 